In the drilling of wells, such as oil wells, it is often necessary or desirable to have information concerning the orientation of the drill string. For example, orientation measurements can be made to determine the amount of deviation of the hole from the vertical. Measurements can also be made to determine the direction of the tool face in relation to the low side of the hole. Instruments for making one or the other of the orientation measurements of this type are well known and are commercially available from the assignee of record. In addition, instruments for making one or the other of such orientation measurements are disclosed in the art.
At least some of the orientation measuring tools function satisfactorily. However, in some instances, it is desirable to obtain both such orientation measurements from a well at about the same time. The so-called mud pulse telemetry tools now available are not generally suited for simultaneous employment in the same drill string. For example, signaling of both measurements using the conventional mud-pulsing technique would be difficult or impossible with multiple orientation instruments simultaneously employed in the drill string.